1. Field of the Invention
The present invention relates to a control device for vehicles using a microcomputer in which, upon occurrence of any malfunction or misoperation of the microcomputer, the control mode is fixed to a fallback mode to avert any erroneous control and prevent the vehicle from falling into a dangerous running condition and thereby to avert danger.
2. Description of the Prior Art
While a microcomputer (hereinafter referred to simply as a CPU) has come into use in various control systems for vehicles, if the CPU fails to operate properly, particularly, if the CPU used in an automotive engine control system malfunctions or misoperates, not only proper control of the engine is lost to cause a bad effect on the engine, but also there arises a case where the vehicle falls into a dangerous running condition. A conventional control system is equipped with a CPU which generates a predetermined on-off signal to be used for the purpose of detecting a malfunction occurring in or misoperation by the CPU and, upon detection of the malfunction of or misoperation by the CPU, generates a reset signal to effect the initialization and restart of the CPU, thereby making it possible to monitor the operation of the control system.
However, if a failure occurs in the hardware of the CPU or the above-described method fails, for some reason, to cause the initialization and restart of the CPU, thereby failing to restore a normal operation of the CPU, the vehicle is still left in a dangerous condition.
The present invention has been made with a view to overcoming the foregoing drawback of the prior art safety device.